Process cartridge and electrophotographic image forming apparatus

ABSTRACT

A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein the main assembly includes a motor, a main assembly side gear for receiving driving force from the motor and a hole defined by twisted surfaces, the hole being substantially coaxial with the gear, the process cartridge includes an electrophotographic photosensitive drum; process means actable on the photosensitive drum; and a projection engageable with the twisted surfaces, the projection being provided at a longitudinal end of the photosensitive drum, wherein the projection is non-twisted, and when the main assembly side gear rotates with the hole and projection engaged with each other, rotational driving force is transmitted from the gear to the photosensitive drum through engagement between the hole and the projection.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a process cartridge and anelectrophotographic image forming apparatus.

Here, the electrophotographic image forming apparatus forms an image ona recording material using an electrophotographic image formationprocess. Examples of the electrophotographic image forming apparatusincludes an electrophotographic copying machine, an electrophotographicprinter (laser beam printer, LED printer or the like), a facsimilemachine and a word processor or the like.

The process cartridge contains integrally electrophotographicphotosensitive member and charging means, developing means or cleaningmeans, and is detachably mountable relative to a main assembly of theimage forming apparatus. It may integrally contain theelectrophotographic photosensitive member and at least one of thecharging means, the developing means and the cleaning means. As anotherexample, it may contain the electrophotographic photosensitive memberand at least the developing means.

In an electrophotographic image forming apparatus using anelectrophotographic image forming process, the process cartridge isused, which contains the electrophotographic photosensitive member andprocess means actable on said electrophotographic photosensitive member,and which is detachably mountable as a unit to a main assembly of theimage forming apparatus (process cartridge type). With this processcartridge type, the maintenance of the apparatus can be carried out ineffect by the user without depending on a serviceman. Therefore, theprocess cartridge type is now widely used in electrophotographic imageforming apparatuses.

The present invention is directed to a further improvement of such aprocess cartridge.

A driving system for a photosensitive member in a process cartridgetype, is disclosed in U.S. Pat. Nos. 4,829,335 and 5,023,660.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide a process cartridge and an electrophotographic image formingapparatus wherein the rotation accuracy of an electrophotographicphotosensitive drum is improved.

It is another object of the present invention to provide a processcartridge and an electrophotographic image forming apparatus whereindriving force is transmitted by abutment between a projection and anedge of a hole.

It is a further object of the present invention to provide a processcartridge and an electrophotographic image forming apparatus whereinengagement between a projection and a hole is firm.

It is a further object of the present invention to provide a processcartridge and an electrophotographic image forming apparatus whereindriving force is transmitted to an electrophotographic photosensitivedrum by engagement between a non-twisted projection and a twisted hole.

It is a further object of the present invention to provide a processcartridge and an electrophotographic image forming apparatus wherein aprojection is engageable with twisted surfaces, and the projection isprovided at a longitudinal end of a photosensitive drum, wherein theprojection is not twisted, and when a main assembly side gear rotateswith the hole and projection engaged with each other, rotational drivingforce is transmitted from the gear to the the photosensitive drumthrough engagement between the hole and the projection.

It is a further object of the present invention to provide a processcartridge and an electrophotographic image forming apparatus wherein aprojection is engageable with twisted surfaces, and the projection isprovided at a longitudinal end of a photosensitive drum, wherein theprojection is not twisted, and when a main assembly side gear rotateswith the hole and projection engaged with each other, rotational drivingforce is transmitted from the gear to the the photosensitive drumthrough engagement between the hole and the projection, and wherein theprojection is not pulled by the hole.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section of an electrophotographic image formingapparatus.

FIG. 2 is an external perspective view of the apparatus illustrated inFIG. 1.

FIG. 3 is a cross-section of a process cartridge.

FIG. 4 is an external perspective view of the process cartridgeillustrated in FIG. 3, as seen from the top right direction.

FIG. 5 is the right-hand side view of the process cartridge illustratedin FIG. 3.

FIG. 6 is the left-hand side view of the process cartridge illustratedin FIG. 3.

FIG. 7 is an external perspective view of the process cartridgeillustrated in FIG. 3, as seen from the top left direction.

FIG. 8 is an external perspective view of the bottom left side of theprocess cartridge illustrated in FIG. 3.

FIG. 9 is an external perspective view of the process cartridgeaccommodating portion of the main assembly of the apparatus illustratedin FIG. 1.

FIG. 10 is an external perspective view of the process cartridgeaccommodating portion of the main assembly of the apparatus illustratedin FIG. 1.

FIG. 11 is a vertical section of a photosensitive drum and a drivingmechanism for driving the photosensitive drum.

FIG. 12 is a perspective view of a cleaning unit.

FIG. 13 is a perspective view of an image developing unit.

FIG. 14 is a perspective view of a drum flange (driving forcetransmitting part) according to a first embodiment.

FIG. 15 is a perspective view of a photosensitive drum according toEmbodiment 1 of the present invention.

FIG. 16 is a perspective view of a side shaft coupling portion of aprocess cartridge according to Embodiment 1 of the present invention.

FIG. 17 is a perspective view of a shaft coupling used in the processcartridge and the main assembly of the electrophotographic image formingapparatus according to Embodiment 1 of the present invention.

FIG. 18 is a cross-sectional view of a driving system provided in themain assembly of the electrophotographic image forming apparatusaccording to Embodiment 1 of the present invention.

FIG. 19 is a perspective view of a shaft coupling member provided in theprocess cartridge and the shaft coupling member provided in the mainassembly of the apparatus according to Embodiment 1 of the presentinvention.

FIG. 20 is a perspective view of a coupling provided in the processcartridge and a shaft coupling member provided in the main assembly ofthe apparatus according to Embodiment 1 of the present invention.

FIG. 21 is a longitudinal sectional view of a coupling portion and acover of the main assembly of the apparatus according to Embodiment 1 ofthe present invention.

FIG. 22 is a side view of a structure of a female coupling shaftaccording to an embodiment of the present invention.

FIG. 23 is a side view showing the structure around the female couplingshaft when the mounting-and-demounting of the process cartridge ismounted to or demounted from the main assembly of the apparatusaccording to Embodiment 1 of the present invention.

FIGS. 24(a) and 24(b) are a sectional view taken along a planeperpendicular to the axis of the male coupling projection and recessaccording to Embodiment 1 of the present invention.

FIG. 25 is a perspective view of a male coupling projection according toanother embodiment of the present invention.

FIG. 26 is a perspective view of a male coupling projection according toa further embodiment of the present invention.

FIG. 27 is a perspective view of a male coupling projection according toa further embodiment of the present invention.

FIG. 28 is a sectional view showing a connecting state of the shaftcoupling between the process cartridge and the main assembly of theapparatus.

FIG. 29 is a perspective view of a male coupling projection according toa further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the embodiments of the present invention will be describedwith reference to the drawings.

Next, desirable embodiments of the present invention will be described.In the following description, the “widthwise” direction of a processcartridge B means the direction in which the process cartridge B isinstalled into, or removed from, the main assembly of an image formingapparatus, and coincides with the direction in which a recording mediumis conveyed. The “lengthwise” direction of the process cartridge B meansa direction which is intersectional with (substantially perpendicularto) the direction in which the process cartridge B is installed into, orremoved from, the main assembly 14. The process catridge B is parallelto the surface of the recording medium, and intersectional with(substantially perpendicular to) the direction in which the recordingmedium is conveyed. Further, the “left” or “right” means the left orright relative to the direction in which the recording medium isconveyed, as seen from above.

FIG. 1 is an electrophotographic image forming apparatus (laser beamprinter) which embodies the present invention, depicting the generalstructure thereof; FIG. 2, an external perspective thereof; and FIGS.3-8 are drawings of process cartridges which embody the presentinvention. More specifically, FIG. 3 is a cross-section of a processcartridge; FIG. 4, an external perspective view of the processcartridge; FIG. 5, a right-hand side view of the process cartridge; FIG.6, a left-hand side view of the process cartridge; FIG. 7, a perspectiveview of the process cartridge as seen from the top left direction; andFIG. 8 is a perspective view of the process cartridge as seen from thebottom left direction. In the following description, the “top” surfaceof the process cartridge B means the surface which faces upward when theprocess cartridge B is in the main assembly 14 of the image formingapparatus, and the “bottom” surface means the surface which facesdownward.

(Electrophotographic Image Forming Apparatus A and Process Cartridge B)

First, referring to FIGS. 1 and 2, a laser beam printer A as anelectrophotographic image forming apparatus which embodies the presentinvention will be described. FIG. 3 is a cross-section of a processcartridge which also embodies the present invention.

Referring to FIG. 1, the laser beam printer A is an apparatus whichforms an image on a recording medium (for example, recording sheet, OHPsheet, and fabric) through an electrophotographic image forming process.It forms a toner image on an electrophotographic photosensitive drum(hereinafter, photosensitive drum) in the form of a drum. Morespecifically, the photosensitive drum is charged with the use of acharging means, and a laser beam modulated with the image data of atarget image is projected from an optical means onto the chargedperipheral surface of the photosensitive drum, forming thereon a latentimage in accordance with the image data. This latent image is developedinto a toner image by a developing means. Meanwhile, a recording medium2 placed in a sheet feeding cassette 3 a is reversed and conveyed by apickup roller 3 b, a conveyer roller pairs 3 c and 3 d, and registerroller pair 3 e, in synchronism with the toner formation. Then, voltageis applied to an image transferring roller 4 as a means for transferringthe toner image formed on the photosensitive drum 7 of the processcartridge B, whereby the toner image is transferred onto the recordingmedium 2. Thereafter, the recording medium 2, onto which the toner imagehas been transferred, is conveyed to a fixing means 5 by guidingconveyer 3 f. The fixing means 5 has a driving roller 5 c, and a fixingroller 5 b containing a heater 5 a, and applies heat and pressure to therecording medium 2 as the recording medium 2 is passed through thefixing means 5, so that the image having been transferred onto therecording medium 2 is fixed to the recording medium 2. Then, therecording medium 2 is conveyed farther, and is discharged into adelivery tray 6 through a reversing path 3 j, by discharging rollerpairs 3 g, 3 h and 3 i. The delivery tray 6 is located at the top of themain assembly 14 of the image forming apparatus A. It should be notedhere that a pivotable flapper 3 k may be operated in coordination with adischarge roller pair 3 m to discharge the recording medium 2 withoutpassing it through the reversing path 3 j. The pickup roller 3 b,conveyer roller pairs 3 c and 3 d, register roller pair 3 e, guidingconveyer 3 f, discharge roller pairs 3 g, 3 h and 3 i, and dischargeroller pair 3 m constitute a conveying means 3.

Referring to FIGS. 3-8, in the process cartridge B, on the other hand,the photosensitive drum 7 with a photosensitive layer 7 e (FIG. 11) isrotated to uniformly charge its surface by applying voltage to thecharging roller 8 as a photosensitive drum charging means. Then, a laserbeam modulated with the image data is projected onto the photosensitivedrum 7 from the optical system 1 through an exposure opening 1 e,forming a latent image on the photosensitive drum 7. The thus formedlatent image is developed with the use of toner and the developing means9. More specifically, the charging roller 8 is disposed in contact withthe photosensitive drum 7 to charge the photosensitive drum 7. It isrotated by the rotation of the photosensitive drum 7. The developingmeans 9 provides the peripheral surface area (area to be developed) ofthe photosensitive drum 7 with toner so that the latent image formed onthe photosensitive drum 7 is developed. The optical system 1 comprises alaser diode 1 a, a polygon mirror 1 b, a lens 1 c, and a deflectivemirror 1 d.

In the developing means 9, the toner contained in a toner container 11Ais delivered to an developing roller 9 c by the rotation of a tonerfeeding member 9 b. The developing roller 9 c contains a stationarymagnet. It is also rotated so that a layer of toner with triboelectriccharge is formed on the peripheral surface of the developing roller 9 c.The image developing area of the photosensitive drum 7 is provided withthe toner from this toner layer, the toner is transferred onto theperipheral surface of the photosensitive drum 7 in a manner to reflectthe latent image, visualizing the latent image as a toner image. Thedeveloping blade 9 d is a blade which regulates the amount of the toneradhered to the peripheral surface of the developing roller 9 c and alsotriboelectrically charges the toner. Adjacent to the developing roller 9e, a toner stirring member 9 c is rotatively disposed to circulativelystir the toner within the image developing chamber.

After the toner image formed on the photosensitive drum 7 is transferredonto the recording medium 2 by applying voltage with polarity oppositeto that of the toner image to the image transferring roller 4, theresidual toner on the photosensitive drum 7 is removed by the cleaningmeans 10. The cleaning means 10 comprises an elastic cleaning blade 10 adisposed in contact with the photosensitive drum 7, and the tonerremaining on the photosensitive drum 7 is scraped off by the elasticcleaning blade 10 a, being collected into a waste toner collector 10 b.

The process cartridge B is formed in the following manner. First, atoner chamber frame 11 which comprises a toner container (toner storingportion) 11A for storing toner is joined with an image developingchamber frame 12 which houses the image developing means 9 such as animage developing roller 9 c, and then, a cleaning chamber frame 13, inwhich the photosensitive drum 7, the cleaning means 10 such as thecleaning blade 10 a, and the charging roller 8 are mounted, is joinedwith the preceding two frames 11 and 12 to complete the processcartridge B. The thus formed process cartridge B is removablyinstallable into the main assembly 14 of the image forming apparatus A.

The process cartridge B is provided with an exposure opening throughwhich a light beam modulated with image data is projected onto thephotosensitive drum 7, and a transfer opening 13 n through which thephotosensitive drum 7 opposes the recording medium 2. The exposureopening 1 e is a part of the cleaning chamber frame 11, and the transferopening 13 n is located between the image developing chamber frame 12and the cleaning chamber frame 13.

Next, the structure of the housing of the process cartridge B in thisembodiment will be described.

The process cartridge in this embodiment is formed in the followingmanner. First the toner chamber frame 11 and the image developingchamber frame 12 are joined, and then, the cleaning chamber frame 13 isrotatively joined with the preceding two frames 11 and 12 to completethe housing. In this housing, the aforementioned photosensitive drum 7,charging roller 8, developing means 9, cleaning means 10, and the like,are mounted to complete the process cartridge B. The thus formed processcartridge B is removably installable into the cartridge accommodatingmeans provided in the main assembly 14 of an image forming apparatus.

(Housing Structure of Process Cartridge B)

As described above, the housing of the process cartridge B in thisembodiment is formed by joining the toner chamber frame 11, the imagedeveloping chamber frame 12, and the cleaning chamber frame 13. Next,the structure of the thus formed housing will be described.

Referring to FIGS. 3 and 20, in the toner chamber frame 11, the tonerfeeding member 9 b is rotatively mounted. In the image developingchamber frame 12, the image developing roller 9 c and the developingblade 9 d are mounted, and adjacent to the developing roller 9 e, thestirring member 9 c is rotatively mounted to circulatively stir thetoner within the image developing chamber. Referring to FIGS. 3 and 19,in the image developing chamber frame 12, a rod antenna 9 h is mounted,extending in the lengthwise direction of the developing roller 9 csubstantially in parallel to the developing roller 9 c. The tonerchamber frame 11 and the development chamber frame 12, which areequipped in the above-described manner, are welded together (in thisembodiment, by ultrasonic wave) to form a second frame which constitutesan image developing unit D (FIG. 13).

The image developing unit of the process cartridge B is provided with adrum shutter assembly 18, which covers the photosensitive drum 7 toprevent it from being exposed to light for an extend period of time orfrom coming in contact with foreign objects when or after the processcartridge B is removed from the main assembly 14 of an image formingapparatus.

Referring to FIG. 6, the drum shutter assembly 18 has a shutter cover 18a which covers or exposes the transfer opening 13 n illustrated in FIG.3, and linking members 18 b and 18 c which support the shutter cover 18.On the upstream side relative to the direction in which the recordingmedium 2 is conveyed, one end of the right-hand side linking member 18 cis fitted in a hole 40 g of a developing means gear holder 40 as shownin FIGS. 4 and 5, and one end of the left-hand side linking member 18 cis fitted in a boss 11 h of the bottom portion 11 b of the toner chamberframe 11. The other ends of the left- and right-hand linking members 18c are attached to the corresponding lengthwise ends of the shutter cover18 a, on the upstream side relative to the recording medium conveyingdirection. The linking member 18 c is made of metallic rod. Actually,the left- and right-hand linking members 18 c are connected through theshutter cover 18 a; in other words, the left- and right-hand linkingmembers 18 c are the left- and right-hand ends of a single piece linkingmember 18 c. The linking member 18 b is provided only on one lengthwiseend of the shutter cover 18 a. One end of the linking member 18 b isattached to the shutter cover 18 a, on the downstream side, relative tothe recording medium conveying direction, of the position at which thelinking member 18 c is attached to the shutter cover 18 a, and the otherend of the linking member 18 b is fitted around a dowel 12 d of theimage development chamber frame 12. The linking member 18 b is formed ofsynthetic resin.

The linking members 18 b and 18 c, which are different in length, form afour piece linkage structure in conjunction with the shutter cover 18 aand the toner chamber frame 11. As the process cartridge B is insertedinto an image forming apparatus, the portion 18 c 1 of the linkingmember 18 c, which projects away from the process cartridge B, comes incontact with the stationary contact member (unillustrated) provided onthe lateral wall of the cartridge accommodating space S of the mainsassembly 14 of the image forming apparatus, and activates the drumshutter assembly 18 to open the shutter cover 18 a.

The drum shutter assembly 18, constituted of the shutter cover 18 a andthe linking members 18 b and 18 c, is loaded with the pressure from anunillustrated torsional coil spring fitted around a dowel 12 d. One endof the spring is anchored to the linking member 18 b, and the other endis anchored to the image developing chamber frame 12, so that thepressure is generated in the direction to cause the shutter cover 18 ato cover the transfer opening 13 n.

Referring again to FIGS. 3 and 12, the cleaning means frame 13 is fittedwith the photosensitive drum 7, the charging roller 8, and the variouscomponents of the cleaning means 10, to form a first frame as a cleaningunit C (FIG. 12).

Then, the aforementioned image developing unit D and cleaning unit C arejoined with the use of a joining member 22, in a mutually pivotablemanner, to complete the process cartridge B. More specifically,referring to FIG. 13, both lengthwise (axial direction of the developingroller 9 c) ends of the image developing chamber frame 12 are providedwith an arm portion 19, which is provided with a round hole 20 which isin parallel to the developing roller 9 c. On the other hand, a recessedportion 21 for accommodating the arm portion 19 is provided at eachlengthwise end of the cleaning chamber frame (FIG. 12). The arm portion19 is inserted in this recessed portion 21, and the joining member 22 ispressed into the mounting hole 13 e of the cleaning chamber frame 13,put through the hole 20 of the end portion of the arm portion 19, andpressed, farther, into the hole 13 e of an partitioning wall 13 t, sothat the image developing unit D and the cleaning unit C are joined tobe pivotable relative to each other about the joining member 22. Injoining the image developing unit D and the cleaning unit C, acompression type coil spring 22 a is placed between the two units, withone end of the coil spring being fitted around an unillustrated dowelerected from the base portion of the arm portion 19, and the other endbeing pressed against the top wall of the recessed portion 21 of thecleaning chamber frame 13. As a result, the image developing chamberframe 12 is pressed downward to reliably keep the developing roller 9 cpressed downward toward the photosensitive drum 7. More specifically,referring to FIG. 13, a roller 9 i having a diameter larger than that ofthe developing roller 9 c is attached to each lengthwise end of thedeveloping roller 9 c, and this roller 9 i is pressed on thephotosensitive drum 7 to maintain a predetermined gap (approximately 300μm) between the photosensitive drum 7 and the developing roller 9 c. Thetop surface of the recessed portion 21 of the cleaning chamber frame 13is slanted so that the compression type coil spring 22 a is graduallycompressed when the image developing unit D and the cleaning unit C areunited. That is, the image developing unit D and the cleaning unit C arepivotable toward each other about the joining member 22, wherein thepositional relationship (gap) between the peripheral surface of thephotosensitive drum 7 and the peripheral surface of the developingroller 9 c is precisely maintained by the elastic force of thecompression type coil spring 2 a.

Since the compression type coil spring 22 a is attached to the baseportion of the arm portion 19 of the image developing chamber frame 12,the elastic force of the compression type coil spring 22 a affectsnowhere but the base portion of the arm portion 19. In a case in whichthe image developing chamber frame 12 is provided with a dedicatedspring mount for the compression type coil spring 22 a, the adjacenciesof the spring seat must be reinforced to precisely maintain thepredetermined gap between the photosensitive drum 7 and the developingroller 9 c. However, with the placement of the compression type coilspring 22 a in the above described manner, it is unnecessary toreinforce the adjacencies of the spring seat, that is, the adjacenciesof the base portion of the arm portion 19 in the case of thisembodiment, because the base portion of the arm portion 19 is inherentlygreater in strength and rigidity.

The above described structure which holds together the cleaning chamberframe 13 and the image developing chamber frame 12 will be describedlater in more detail.

(Structure of Process Cartridge B Guiding Means)

Next, the means for guiding the process cartridge B when the processcartridge B is installed into, or removed from, the main assembly 14 ofan image forming apparatus. This guiding means is illustrated in FIGS. 9and 10. FIG. 9 is a perspective view of the left-hand side of theguiding means, as seen (in the direction of an arrow mark X) from theside from which the process cartridge B is installed into the mainassembly 14 of the image forming apparatus A (as seen from the side ofthe image developing unit D side). FIG. 10 is a perspective view of theright-hand side of the same, as seen from the same side.

Referring to FIGS. 4, 5, 6 and 7, each lengthwise end of the cleaningframe portion 13 is provided with means which serves as a guide when theprocess cartridge B is installed into, or removed from, the apparatusmain assembly 14. This guiding means is constituted of a cylindricalguides 13 aR and 13 aL as a cartridge positioning guiding member, androtation controlling guides 13 bR and 13 bL as means for controlling theattitude of the process cartridge B when the process cartridge B isinstalled or removed.

As illustrated in FIG. 5, the cylindrical guide 13 aR is a hollowcylindrical member. The rotation controlling guides 13 bR is integrallyformed together with the cylindrical guide 13 aR, and radially protrudesfrom the peripheral surface of the cylindrical guide 13 aR. Thecylindrical guide 13 aR is provided with a mounting flange 13 aR1 whichis also integral with the cylindrical guide 13 aR. Thus, the cylindricalguide 13 aR, the rotation controlling guide 13 bR, and the mountingflange 13 aR1 constitute the right-hand side guiding member 13R, whichis fixed to the cleaning chamber frame 13 with small screws put throughthe screw holes of the mounting flange 13 aR1. With the right-hand sideguiding member 13R being fixed to the cleaning chamber frame 13, therotation controlling guide 13 bR extends over the lateral wall of thedeveloping means gear holder 40 fixed to the image developing chamberframe 12.

Referring to FIG. 11, a drum shaft member is constituted of a drum shaftportion 7 a inclusive of a larger diameter portion 7 a 2, a disk-shapedflange portion 29 and a cylindrical guide portion 13 aL. The largerdiameter portion 7 a 2 is fitted in the hole 13 k 1 of the cleaningframe portion 13. The flange portion 29 is engaged with a positioningpin 13 c projecting from the side wall of the lengthwise end wall of thecleaning frame portion 13, being prevented from rotating, and is fixedto the cleaning frame portion 13 with the use of small screws 13 d. Thecylindrical guide 13 aL projects outward (toward front, that is, thedirection perpendicular to the page of FIG. 6). The aforementionedstationary drum shaft 7 a which rotatively supports a spur gear 7 nfitted around the photosensitive drum 7 projects inwardly from theflange 29 (FIG. 11). The cylindrical guide 13 aL and the drum shaft 7 aare coaxial. The flange 29, the cylindrical guide 13 aL, and the drumshaft 7 a, are integrally formed of metallic material such as steel.

Referring to FIG. 6, there is a rotation controlling guide 13 bLslightly away from the cylindrical guide 13 aL. It is long and narrow,extending substantially in the radial direction of the cylindrical guide13 aL and also projecting outward from the cleaning chamber frame 13. Itis integrally formed with the cleaning chamber frame 13. In order toaccommodate this rotation controlling guide 13 bL, the flange 29 isprovided with a cutaway portion. The distance the rotation controllingguide 13 bL projects outward is such that its end surface issubstantially even with the end surface of the cylindrical guide 13 aL.The rotation controlling guide 13 bL extends over the side wall of thedeveloping roller bearing box 9 v fixed to the image developing chamberframe 12. As is evident from the above description, the left-hand sideguiding member 13L is constituted of separate two pieces: the metalliccylindrical guide 13 aL and the rotation controlling guide 13 bL ofsynthetic resin.

Next, a regulatory contact portion 13 j, which is a part of the topsurface of the cleaning chamber frame 13, will be described. In thefollowing description of the regulatory contact portion 13 j, “topsurface” means the surface which faces upward when the process cartridgeB is in the main assembly 14 of an image forming apparatus.

Referring to FIGS. 4-7, two portions 13 j of the top surface and 13 i ofthe cleaning unit C, which are the portions right next to the right andleft front corners 13 p and 13 q, relative to the directionperpendicular to the direction in which the process cartridge B isinserted, constitute the regulatory contact portions 13 j, whichregulate the position and attitude of the process cartridge B when thecartridge B is installed into the main assembly 14. In other words, whenthe process cartridge B is installed into the main assembly 14, theregulatory contact portion 13 j comes in contact with the fixed contactmember 25 provided in the main assembly 14 of an image forming apparatus(FIGS. 9 and 10), and regulates the rotation of the process cartridge Babout the cylindrical guide 13 aR and 13 aL.

Next, the guiding means on the main assembly side 14 will be described.Referring to FIG. 1, as the lid 35 of the main assembly 14 of an imageforming apparatus is pivotally opened about a supporting point 35 a inthe counterclockwise direction, the top portion of the main assembly 14is exposed, and the process cartridge accommodating portion appears asillustrated in FIGS. 9 and 10. The left and right internal walls of theimage forming apparatus main assembly 14, relative to the direction inwhich the process cartridge B is inserted, are provided with guidemembers 16L (FIG. 9) and 16R (FIG. 10), respectively, which extenddiagonally downward from the side opposite to the supporting point 35 a.

As shown in the drawings, the guide members 116L and 116R comprise guideportions 116 a and 116 c, and positioning grooves 116 b and 116 dconnected to the guide portions 116 a and 116 c, respectively. The guideportions 116 a and 116 c extend diagonally downward, as seen from thedirection indicated by an arrow mark X, that is, the direction in whichthe process cartridge B is inserted. The positioning grooves 116 b and116 d have a semicircular cross-section which perfectly matches thecross-section of the cylindrical guides 13 aL or 13 aR of the processcartridge B. After the process cartridge B is completely installed inthe apparatus main assembly 14, the centers of semicircularcross-sections of the positioning groove 16 b and 16 d coincide with theaxial lines of the cylindrical guides 13 aL and 13 aR, respectively, ofthe process cartridge B, and hence, with the axial line of thephotosensitive drum 7.

The width of the guide portions 116 a and 116 c as seen from thedirection in which the process cartridge B is installed or removed iswide enough to allow the cylindrical guides 13 aL and 13 aR to ride onthem with a reasonable amount of play. Therefore, the rotationcontrolling guides 13 bL and 13 bR which are narrower than the diameterof the cylindrical guides 13 aL and 13 aR naturally fit more loosely inthe guide portions 116 a and 116 c than the cylindrical guides 13 aL and13 aR, respectively, yet their rotation is controlled by the guideportions 116 a and 116 c. In other words, when the process cartridge Bis installed, the angle of the process cartridge B is kept within apredetermined range. After the process cartridge B is installed in theimage forming apparatus main assembly 14, the cylindrical guides 13 aLand 13 aR of the process cartridge B are in engagement with thepositioning grooves 116 b and 116 d of the guiding members 13L and 13R,and the left and right regulatory contact portions 13 j located at thefront portion, relative to the cartridge inserting direction, of thecleaning chamber frame 13 of the process cartridge B, are in contactwith the fixed positioning members 25, respectively.

The weight distribution of the process cartridge B is such that when theline which coincides with the axial lines of the cylindrical guides 13aL and 13 aR is level, the image developing unit D side of the processcartridge B generates larger movement about this line than the cleaningunit C side.

The process cartridge B is installed into the image forming apparatusmain assembly 14 in the following manner. First, the cylindrical guides13 aL and 13 aR of the process cartridge B are inserted into the guideportion 116 a and 116 c, respectively, of the cartridge accommodatingportion in the image forming apparatus main assembly 14 by grasping therecessed portion 17 and ribbed portion 11 c of the process cartridge Bwith one hand, and the rotation controlling guides 13 bL and 13 bR arealso inserted into the guide portions 116 a and 116 c, tilting downwardthe front portion, relative to the inserting direction, of the processcartridge B. Then, the process cartridge B is inserted farther with thecylindrical guides 13 aL and 13 aR and the rotation controlling guides13 bL and 13 bR of the process cartridge B following the guide portions116 a and 116 c, respectively, until the cylindrical guides 13 aL and 13aR reach the positioning grooves 116 b and 116 d of the image formingapparatus main assembly 14. Then, the cylindrical guides 13 aL and 13 aRbecome seated in the positioning grooves 116 b and 116 d, respectively,due to the weight of the process cartridge B itself; the cylindricalguides 13 aL and 13 aR of the process cartridge B are accuratelypositioned relative to the positioning grooves 116 b and 116 d. In thiscondition, the line which coincides with the axial lines of thecylindrical guides 13 aL and 13 aR also coincides with the axial line ofthe photosensitive drum 7, and therefore, the photosensitive drum 7 isreasonably accurately positioned relative to the image forming apparatusmain assembly 14. It should be noted here that the final positioning ofthe photosensitive drum 7 relative to the image forming apparatus mainassembly 14 occurs at the same time as the coupling between the two iscompleted.

Also in this condition, there is a slight gap between the stationarypositioning member 25 of the image forming apparatus main assembly 14and the regulatory contact portion 13 j of the process cartridge B. Atthis point of time, the process cartridge B is released from the hand.Then, the process cartridge B rotates about the cylindrical guides 13 aLand 13 aR in the direction to lower the image developing unit D side andraise the cleaning unit C side until the regulatory contact portions 13j of the process cartridge B come in contact with the correspondingstationary positioning members 25. As a result, the process cartridge Bis accurately positioned relative to the image forming apparatus mainassembly 14. Thereafter, the lid 35 is closed by rotating it clockwiseabout the supporting point 35 a.

In order to remove the process cartridge B from the apparatus mainassembly 14, the above described steps are carried out in reverse. Morespecifically, first, the lid 35 of the apparatus main assembly 14 isopened, and the process cartridge B is pulled upward by grasping theaforementioned top and bottom ribbed portions 11 c, that is, thehandhold portions, of the process cartridge by hand. Then, thecylindrical guides 13 aL and 13 aR of the process cartridge B rotate inthe positioning grooves 116 b and 116 d of the apparatus main assembly14. As a result, the regulatory contact portions 13 j of the processcartridge B separate from the corresponding stationary positioningmember 25. Next, the process cartridge B is pulled more. Then, thecylindrical guides 13 aL and 13 aR come out of the positioning grooves116 b and 116 d, and move into the guide portions 116 a and 116 c of theguiding members 116L and 116R, respectively, fixed to the apparatus mainassembly 14. In this condition, the process cartridge B is pulled more.Then, the cylindrical guides 13 aL and 13 aR and the rotationcontrolling guides 13 bL and 13 bR of the process cartridge B slidediagonally upward through the guide portions 116 a and 116 c of theapparatus main assembly 14, with the angle of the process cartridge Bbeing controlled so that the process cartridge B can be completely movedout of the apparatus main assembly 14 without making contact with theportions other than the guide portions 116 a and 116 c.

Referring to FIG. 12, the spur gear 7 n is fitted around one of thelengthwise ends of the photosensitive drum 7, which is the end oppositeto where the helical drum gear 7 f is fitted. As the process cartridge Bis inserted into the apparatus main assembly 14, the spur gear 7 nmeshes with a gear (unillustrated) coaxial with the image transferringroller 4 located in the apparatus main assembly, and transmits from theprocess cartridge B to the transferring roller 4 the driving force whichrotates the transferring roller 4.

(Coupling and Driving Structure)

The description will be made as to the structure of the shaft couplingapparatus which is a drive transmission mechanism from the main assemblyof the image forming apparatus to the process cartridge.

FIG. 14 is a perspective view of a drum flange 16 as a driving forcetransmission part integral with the male coupling shaft 17; FIG. 15 is apartly sectional perspective view of the photosensitive drum 7 mountedto the drum flange 16; FIG. 16 is an enlarged perspective view aroundthe male coupling shaft 17 of the process cartridge B shown in FIG. 11;and FIG. 17 is an illustration of a relation between the male couplingshaft 17 (provided in the process cartridge B) as the shaft couplingmember and the female coupling shaft 18 (provision in the main assembly13).

As shown in FIG. 11, and FIG. 15 to FIG. 17, a process cartridge shaftcoupling means is provided at one longitudinal end of the photosensitivedrum 7 mounted to the process cartridge B. The shaft coupling means isin the form of a male coupling shaft 17 (circular column configuration)on a drum flange 16 fixed to one end of the photosensitive drum 7, andhas a projection 17 a formed at a free end of the male coupling shaft17. The male coupling shaft 17 is engaged in a bearing 24 and shaftreception 24 a as a drum shaft. In this example, the drum flange 16,male coupling shaft 17 and the projection 17 a are integrally formed.The drum flange 16 is integrally provided with a helical drum gear 16 ato transmit the driving force to the developing roller 10 d in theprocess cartridge B. Therefore, as shown in FIG. 14, the drum flange 16is an integrally molded product of plastic resin material having ahelical gear 16 a, coupling male shaft 17, and the projection 17 a andthe engaging member 16 b, which will be described hereinafter, toconstitute a driving force transmitting part having a function oftransmitting a driving force.

The projection 17 a has a configuration of non-twisted prism, and moreparticularly, it has a cross-section of substantially equilateraltriangle, and the recess 18 a engageable with the projection 17 a is atwisted hole having a section of substantially equilateral triangle. Therecess 18 a rotates integrally with a large gear 34 provided in the mainassembly 13 of the apparatus. With the structure of this embodiment, theprocess cartridge B is mounted to the main assembly 13, and theprojection 17 a and the recess 18 a of the main assembly 13 are broughtinto engagement with each other. When the rotating force is transmittedfrom the recess 18 a to the projection 17 a, the edge lines of theequilateral triangular prism of the projection 17 a are contacted to theedge 18 a 1 of the equilateral triangle of the recess 18 a at theentrance. Therefore, the axes are substantially aligned (FIGS. 24, 28).As described in the foregoing, by a leaf spring 41 provided on theapparatus guiding member 15 of the main assembly 13, the processcartridge B is urged toward the driving side in the axial direction ofthe photosensitive drum 7. Thus, the photosensitive drum 7 integral withthe projection 17 a is stably and correctly positioned both in thelongitudinal direction and radial direction in the main assembly 13. Theleaf spring 41 is not inevitable.

The position of a cross-section of a three dimensional member is stablydetermined by three contact points in a plane perpendicular to the axisthereof, theoretically. When the contact positions 17 a 1 of theprojections 17 a are at apexes of a substantially equilateral trianglein the plane, and the cross-sectional configuration of the recess 18 ais substantially equilateral triangle, then the contact portions 17 a 1of the projection 17 a are contacted to the entrance edges 18 a 1 of theequilateral triangle of the recess 18 a under the same conditions.Therefore, the changes of the contact points and the rotationnon-uniformity of the coupling driving due to the load variation duringthe rotation of the process cartridge B are minimized, thus improvingthe rotation accuracy of the photosensitive drum 7.

FIG. 28 shows an engagement state between the projection 17 a and therecess 18 a. As shown in FIG. 28, when the driving force is transmittedfrom the recess 18 a to the projection 17 a, the neighborhood 17 a 3 ofthe base portion of the projection 17 a (portion closer to the shaftportion 17 than the free end 17 a 2) is contacted to the corner portion(edge) 18 a 4 of the inlet 18 a 3 of the recess 18 a. The projection 17a is not contacted to the inclined surface 18 a 1 of the recess 18 a. Inthis manner, the triangular prism 17 a is engaged with the recess (hole)18 a, and the hole 18 a is rotated. Then, the base portion 17 a 3 of thetriangular prism 17 a is contacted to the corner portion 18 a 4 of theentrance 18 a 3 to the hole 18 a so that position thereof relative tothe hole is determined. Since the base portion has a strength higherthan the other portion, and therefore, the triangular prism (projection)does not deform. The corner portion of the triangular prism and/or thecorner portion of the entrance to the hole is locally deformed so thatcorner portion bites into the inner surface of the hole. Therefore, thecoupling between the recess and the hole is firmer. The advantageouseffects are remarkable when the coupling parts are of plastic resinmaterial.

The male coupling shaft 17 and the projection 17 a are provided on thedrum flange 16 such that when the drum flange 16 is mounted to one endof the photosensitive drum 7, they are coaxial with the photosensitivedrum 7. Designated by is an engaging portion, and is engageable with theinner surface of the drum cylinder 7 a. The fixing of the drum flange 16to the photosensitive drum 107, may be accomplished by crimping orbonding. The circumference of the drum cylinder 7 a is coated with aphotosensitive layer 7 b (FIGS. 11 and 15).

A drum flange 25 is fixed to the other side of the photosensitive drum7. A spur gear 25 b is integrally molded with the drum flange 25. Thedrum flange 25 is rotatably engaged with the drum shaft 7 d integralwith the flange 29 fixed to the cleaning frame 12 c.

When the process cartridge B is mounted to the main assembly 13, thecylindrical guide 13 aL coaxial with the drum shaft 7 d is engaged withthe U shaped groove 116 b (FIG. 9) of the main assembly 13 and iscorrectly positioned, and the spur gear 25 b molded integrally with thedrum flange 25 is engaged with a gear (unshown) for transmitting thedriving force to the transfer roller 4.

Around the projection 17 a of the male coupling shaft 17 of the processcartridge B, there is provided a hollow cylindrical boss 24 a concentricwith the male shaft 17 in the cleaning frame 12 c (FIGS. 4, 11 and 16).When the process cartridge B is mounted to or demounted from the mainassembly, the male coupling projection 17 a is protected by the boss 24a, and therefore, the liability of damage thereto or deformation thereofis reduced. Thus, the vibration or wobbles during the coupling drivingoperation due to the damage of the projection 17 a, can be avoided.

Examples of the material of the drum flanges 16 and 25, the shaft 17 andthe projection 17 a include polyacetal, polycarbonate, polyamide,polybutylene-terephthalate or another resin material. Other materialsare usable and can be selected properly by one skilled in the art.

The boss 24 a also functions as a cylindrical guide 13 aR for theprocess cartridge B when it is mounted to the main assembly 13. When theprocess cartridge B is mounted to the main assembly, the boss 24 a andthe main assembly side guide portion 15 c are abutted, and the boss 24 afunctions as a guiding member for the mounting of the process cartridgeB to the mounting position, thus facilitating themounting-and-demounting of the process cartridge B relative to the mainassembly 13 of the apparatus. When the process cartridge B has beenmounted to the mounting position, said boss 24 a is supported by the Ugroove 116 d which is a recess provided in the guide portion 116 c. Whenthe male coupling shaft 17 and the female shaft 18 are aligned axiallyby the driving force applied upon the image forming operation, the boss24 a is slightly raised from the groove 116 d (approx. 0.3-1.0), whereinthe gap between the boss 24 a and the main assembly guide portion 116 c(U groove 15 d) is smaller than the radial gap between the male couplingprojection 17 a and the recess 18 a. Therefore, the engagement betweenthe male coupling projection 17 a and the recess 18 a is enabled in thestate in which the process cartridge B is mounted to the processcartridge B. A recess 18 a is provided at a rear part of the groove 116d. The configuration of the boss 24 a is not limited to the cylindricalshape of this embodiment, and it is not inevitably complete cylindricalbut may be part-cylindrical provided that it can be guided by the guideportion 116 c and can be supported by the groove 116 d. In thisembodiment, the cylindrical boss 24 a and the bearing 24 for rotatablysupporting the male coupling shaft 17 are integrally molded, and it isthreaded (unshown) to the cleaning frame 12 c (FIG. 11), but this is notinevitable, and the bearing 24 and boss 24 a may be separate members.

In this embodiment, the drum flange 25 is engaged with the drum shaft 7d provided in the cleaning frame 12 c (FIG. 11), and the male couplingshaft 17 is engaged with the inner surface of the bearing 24 provided inthe cleaning frame 12 c; and in this state, the photosensitive drum 7 ismounted to the cleaning frame 12 c of the process cartridge B. Then, thephotosensitive drum 7 is rotated about the drum shaft 7 d and the malecoupling shaft 17. In this embodiment, the photosensitive drum 7 ismounted, for axial movement, to the cleaning frame 12 c. This is done inconsideration of the mounting tolerance. This is not inevitable, andphotosensitive drum 7 may be immovable in the axial direction (forexample, the positioning of the photosensitive drum in the axialdirection, which will be described hereinafter is usable).

On the other hand, the main assembly 13 of the image forming apparatusis provided with a main assembly side shaft coupling apparatus. The mainassembly side shaft coupling apparatus has a female coupling shaft 18(circular column configuration) at a position where the axis of thephotosensitive drum and the rotation axis are coaxial when it is inengagement with the process cartridge side shaft coupling member and isrotated. The female coupling shaft 18, as shown in FIGS. 11, 18, isintegral with the large gear 34 for transmitting the driving force fromthe motor 30 to the photosensitive drum 7. The female coupling shaft 18is projected from a lateral end of the large gear 34 at the center ofrotation of the large gear 34. In this embodiment, the large gear 34 andthe female coupling shaft 18 are integrally produced by a mold.

The large gear 34 provided in the main assembly 13 is a helical gear.When the helical gear receives the driving force from the small gear 20in the form of a helical fixed to the shaft 30 a of the motor 30 shownin FIGS. 11, 18, a thrust force tending to move the female couplingshaft 18 toward the male shaft 17 is produced due to the inclinationdirection and the angle of the teeth. Thus, when the motor 30 is drivenfor image formation, the female coupling shaft 18 is moved toward themale shaft 17 also by the thrust to assist the engagement between therecess 18 a and the projection 17 a. The recess 18 a is formed at thefree end of the female coupling shaft 18 and at the center of rotationof the female coupling shaft 18.

In this embodiment, the driving force is transmitted directly from thesmall gear 20 fixed to the motor shaft 30 a to the large gear 34, butthis is not inevitable, and the use may be made with a gear train toeffect reduced speed drive transmission, a pair of friction rollers, acombination of a timing belt and a pulley, or the like.

(Interrelating Device Between Openable Cover and Shaft Coupling)

Referring to FIGS. 21 to 23, a structure for engaging the recess 18 aand the projection 17 a in interrelation with closing operation of theopenable cover 14 is shown.

As shown in FIG. 23, the large gear 34 66 is fixed between a side plate66 and the side plate 67 in the main assembly 13, and the femalecoupling shaft 18 coaxially integral with the large gear 34 is rotatablysupported by the side plates 67, 66. An outer cam 35 and an inner cam 63are closely inserted into between the large gear 34 and the side plate66. The inner cam 63 is fixed to the side plate 66, and the outer cam 35is rotatably engaged with the female coupling shaft 18. The surfaces ofthe outer cam 35 and the inner cam 63 which are substantiallyperpendicular to the axial direction and which are faced to each other,are cam surfaces, and are screw surfaces coaxial with the femalecoupling shaft 18 and are contacted to each other. Between the largegear 34 and the side plate 67, a compression coil spring 68 iscompressed and fitted around the female coupling shaft 18.

As shown in FIG. 21, an arm 35 a is extended from an outer periphery ofthe outer cam 35 in a radial direction, and an end of the arm 35 a iscoupled with an end of a link 65 by pins 65 a and 65 b at a positionopposite from the opening side when the openable cover 14 is closed.

FIG. 22 is a view as seen from the right side in FIG. 21. When theopenable cover 14 is closed, the link 65, outer cam 35 and the like areat the positions shown in the Figure, where the male coupling projection17 a and the recess 18 a are engaged so that driving force can betransmitted from the large gear 34 to the photosensitive drum 7. Whenthe openable cover 14 is opened, the pin 65 a is rotated upward aboutthe shaft 18 a, so that arm 35 a is pulled up through the link 65, andthe outer cam 35 is rotated; thus, relative sliding motion is causedbetween the outer cam 35 and the inner cam 63 to move the large gear 34away from the photosensitive drum 7. At this time, the large gear 34 ispushed by the outer cam 35, and is moved against the compression coilspring 38 mounted between the side plate 39 and the large gear 34, bywhich the female coupling recess 18 a is disengaged from the malecoupling projection 17 a as shown in FIG. 23 to release the coupling tobring the process cartridge B into demountable state.

On the contrary, when the openable cover 14 is closed, the pin 65 aconnecting the link 65 with the openable cover 14, is rotated downwardabout the shaft 18. The link 37 is moved downward to push the arm 35 adown, so that outer cam 35 is rotated in the opposite direction and ispushed by the compression coil spring 38. By this action, the large gear34 is moved to the left by the spring 38 from a position shown in FIG.23 to a position shown in FIG. 22, so that large gear 34 is set again ata position of FIG. 22, and the female coupling recess 18 a is engagedwith the male coupling projection 17 a to re-establish a drivetransmittable state. Thus, the demountable state and the drivetransmittable state of the process cartridge B are established inresponse to opening and closing of the openable cover 14. When the outercam 35 is rotated in the opposite direction by the closing of theopenable cover 14 to move the large gear 34 to the left from theposition of FIG. 23, the female coupling shaft 18 and the end surface ofthe male coupling shaft 17 may be abutted against each other so thatmale coupling projection 17 a and the female coupling recess 18 a maynot be engaged with each other. However, they will be brought intoengagement as soon as starting of the image forming apparatus A, as willbe described hereinafter.

Thus, in this embodiment, when the process cartridge B is mounted to ordemounted from the main assembly 13 of the apparatus, the openable cover14 is opened. In interrelation with the opening and closing of theopenable cover 14, the female coupling recess 18 a is moved in thehorizontal direction (the direction of arrow j). When the processcartridge B is mounted to or demounted from the main assembly 14, thecoupling (17 a, 18 a) of the main assembly 13 and the process cartridgeB are not to be engaged, and, they should not be engaged. Thus, themounting-and-demounting of the process cartridge B relative to the mainassembly 13 can be carried out smoothly. In this example, the femalecoupling recess 18 a is urged toward the process cartridge B by thelarge gear 34 being urged by the compression coil spring 38. When themale coupling projection 17 a and the recess 18 a are to be brought intoengagement, they may be abutted to each other, and therefore, they arenot properly engaged. When, however, the motor 30 is first rotated afterthe process cartridge B is mounted to the main assembly 13, the femalecoupling recess 18 a is rotated, by which they are instantaneouslybrought into engagement.

(Male Coupling Shaft and Female Shaft)

The function of the projection 17 a and the recess 18 a in the shaftcoupling mechanism, will now be described.

The female coupling shaft 18 provided in the main assembly 13 issupported so as to be movable in the axial direction but not in theradial direction. The process cartridge B is mounted to the mainassembly 13 for movement in the radial direction of the photosensitivedrum 7.

When the process cartridge B is mounted to the main assembly 13 of theapparatus, a cylindrical guide 9 aL coaxial with the drum shaft 7 d(FIG. 11) supporting the drum flange 25 mounted to the otherlongitudinal end of the photosensitive drum 7, enters the U groove 116 b(FIG. 9) in the receptor portion of the main assembly 13 without gap andis correctly positioned, and the spur gear 25 b molded integrally withthe drum flange 25 is brought into meshing engagement with a gear(unshown) for transmitting the driving force to the transfer roller 4.On the other hand, at one longitudinal end (driving side) of thephotosensitive drum 7, a boss 24 a formed on the cleaning frame 13, issupported by U groove 116 d provided in the main assembly 14.

By closing the openable cover 14, the female coupling shaft 18 movestoward the male coupling shaft 17, and if the phases are aligned betweenthe projection 17 a and the recess 18 a, the recess 18 a engages withthe projection 17 a in the axial direction. At this time, if the phasesare not aligned, the end surface 17 a 2 of the male coupling shaft 17abuts the end surface of the female coupling shaft 18 and is pushed bythe spring force of the compression coil spring 38.

Then, the driving side shaft coupling member operates as follows.

When the driving motor 30 is rotated, the female coupling shaft 18 isadvanced by the spring force of the compression coil spring 38 when thephases are aligned between the projection 17 a and the recess 18 a (thephase alignment is reached at each 120° rotation in this embodiment), sothat they are engaged with each other, and the rotating force istransmitted from the main assembly 13 to the process cartridge B.

The projection 17 a smoothly enters the recess 18 a upon the engagementof the shaft coupling with a gap, because the section of the recess 18 a(substantially equilateral triangle) is larger than the projection 17 a,as shown in FIG. 24(a). Thus, static positioning accuracy between themale coupling shaft 17 and the female coupling shaft 18 is not requiredto be strict, but may be rough.

In this embodiment, the projection length of the above-describedcylindrical boss 24 a is larger than the projection length of theprojection 17 a (FIG. 11). When the projection 17 a and the recess 18 aare engaged, the inner surface of the cylindrical boss 24 a is engagedwith the outer peripheral surface of the female coupling shaft 18 tofunction as a guide for the engagement therebetween.

When the female coupling shaft 18 is rotated after the projection 17 aenters the recess 18 a, upon the image formation, the edge 18 a 1 at theentrance of the recess 18 a and the contact portion 17 a 1 of theprojection 17 a are abutted to permit driving force transmission. Atthis time, the male coupling shaft 17 moves instantaneously so that edge18 a 1 at the entrance of the recess 18 a and the contact portion 17 a 1of the projection 17 a are contacted uniformly (from the state shown inFIG. 24(a) to the state shown in FIG. 24(b)). Since the contact portion17 a 1 exists at each of apex points of a substantially equilateraltriangle configuration, the male coupling shaft 17 and the female shaft18 become coaxial when the contact force becomes substantially uniform.More particularly, immediately after the projection 17 a enters therecess 18 a, the center X1 of the projection 17 a and the center X2 ofthe recess 18 a are not aligned (FIG. 24(a)). When the recess 18 astarts to rotate, the inner side thereof is contacted to the threecontact portions 17 a 1 of the projection 17 a, then the centers X1, X2are substantially aligned (FIG. 24(b)).

With such a structure, an automatic axial alignment is carried outbetween the male coupling shaft 17 and the female shaft 18 upon theoperation of the motor 30. By the transmission of the driving force tothe photosensitive drum 7, a rotating force is applied to the processcartridge B. By this, an abutment (portion) 13 j (FIGS. 4, 7) providedat an upper surface of the cleaning frame 12 c of the process cartridgeB is abutted to an abutment portion 26 (FIGS. 9, 10) fixedly provided inthe main assembly 13, so that process cartridge B is correctlypositioned relative to the main assembly 13.

When the driving force is not transmitted (when the image formingoperation is not carried out), a gap is produced between the imageforming apparatus and the recess 18 a in the radial direction, theengagement and disengagement of the shaft coupling and themounting-and-demounting of the process cartridge B relative to the mainassembly 13 are easy. When the driving is effected, the urging force isprovided with stabilization, so that play or vibration there can besuppressed.

In this embodiment, the male coupling projection and recess havesubstantially equilateral triangle shapes, but the same effects can beprovided when they are substantially regular polygonal configuration,and the projection has contact points corresponding to the configurationof the female coupling recess. Substantially regular polygonalconfiguration is desirable since then the positioning can be effectedwith high precision, but this is not limiting,.and another polygonalshape is usable if configuration is such that axial alignment isestablished with axial force.

When the male coupling projection and the recess are compared, theprojection is naturally easily damaged and the strength of theprojection is poorer than the recess. In view of this, this embodimentis such that male coupling projection is provided in the exchangeableprocess cartridge B, and the female coupling recess is provided in themain assembly 13 of the image forming apparatus which is required tohave a higher durability than the process cartridge.

Taking a process cartridge B as an example, this embodiment issummarized as follows. The process cartridge B is detachably mountablerelative to a main assembly 13 of an electrophotographic image formingapparatus A for forming an image of a recording material 2, saidapparatus comprising a motor 30, a large gear 34 for receiving drivingforce from the motor 30, a recess 18 a in the form of a hole of prismconfiguration integrally rotatable with the large gear 34, said holebeing at the center portion of the large gear 34. Said process cartridgeB includes an electrophotographic photosensitive drum 7, process meansactable on the electrophotographic photosensitive drum 7 (chargingroller 8, developing roller 10 d cleaning blade 11 a), a projection 17 aengageable with the recess 18 a and contactable to an inner surfacethereof when the process cartridge B is mounted to the main assembly 13of the apparatus, and the large gear 34 is rotated with the processcartridge B being in engagement with the recess 18 a, the rotating forceis transmitted from the large gear 34 to the electrophotographicphotosensitive drum 7 with the male coupling shaft 17 and the femaleshaft 18 being substantially axially aligned.

The projection 17 a is projected from a free end of a male couplingshaft 17 projected outwardly from the center of rotation of thephotosensitive drum 7 in the longitudinal direction of thephotosensitive drum 7. Here, the male coupling shaft 17 functions torotatably support the photosensitive drum 7 on the cleaning frame 12 c.

The male coupling shaft 17 is provided at the center of the helical gear16 a on one side of the gear, and opposite side of the helical gear 16 ais provided with an engaging portion 16 b for engagement with an innersurface of the electrophotographic photosensitive drum 7. The projection17 a, male coupling projection 17, helical gear 16 a and the engagingportion 16 b are integrally molded from a resin material.

There is provided a cylindrical boss 24 a enclosing the projection 17 aor an arcuate configuration boss extended along a part of the projection17 a. The boss 24 a functions to impart a relative movement between therecess 18 a and the projection 17 a to function as a cylindrical guide13 aR for the engagement therebetween.

More specific embodiments will be described. The module of the largegear 34 of the main assembly 13 of the apparatus is 0.4-0.7. Thededendum diameter of the large gear 34 is approx. 30 mm-150 mm, and theteeth number of the large gear 34 is approx. 40-400. The figures may beproperly selected by one skilled in the art in consideration of thespace in the main assembly 13, the desired quality of the image. Thefigures are not limiting. In this embodiment, the module of the largegear 34 is 0.5, the dedendum diameter is approx. 100, and the teethnumber is 200.

The positioning of the process cartridge B relative to the main assembly13 during the image formation (driving transmission) is summarized asfollows.

The process cartridge B is positioned in the longitudinal direction bythe engagement of the cartridge frame to the cartridge mounting portionof the main assembly 13 when it is mounted to the main assembly 13. Inthe perpendicular direction, the cylindrical guide 13 aL is snuglyfitted in the U groove 116 b so that it is correctly positioned in thatdirection. On the other hand, the boss 24 a is simply supported in the Ugroove 116 b in the receptor portion. During the image formationoperation, (drive transmission), the process cartridge B is positionedsuch that projection 17 a and the recess 18 a are engaged with eachother and are axially aligned. At this time, the boss 24 a is away fromthe groove 116 d. When the openable cover 14 of the main assembly isclosed, the female coupling shaft 18 is moved toward the male shaft 17.When the main assembly motor 30 is rotated, the projection 17 a and therecess 18 a are engaged with axial alignment therebetween, and in theaxial direction, the process cartridge B is positioned by the U groove116 d at one end of the photosensitive drum 7 and by a rotating recess18 a at the other end. The photosensitive drum 7 is movable in itslongitudinal direction (by approx. 0.1 mm-1.0 mm) in consideration of anassembling tolerance. When the photosensitive drum 7 is supported forlongitudinal movement, the axial direction thereof is determinatedrelative to the cleaning frame 12 c, as described in the foregoing. Theprocess cartridge B is mounted to the main assembly, for movement (byapprox. 0.1 mm-3 mm) relative to a plate (mounting guide portions 116 a,116 c) of the main assembly in view of the assembling tolerance, and ismoved in the radial direction of the photosensitive drum 7.

During the image formation operation, the process cartridge B receives arotational force in the rotational direction of the photosensitive drum7, by which the abutment portion 9 j of the process cartridge B isabutted to a fixing member 26 functioning as an abutment in the mainassembly 13.

Accordingly, the process cartridge B is correctly positioned relative tothe main assembly 13 of the apparatus in both the longitudinal directionand the radial direction during the image formation operation.

Further Embodiments

In the foregoing Embodiment 1, the configurations of the projection 17 aof the male coupling shaft 17 and the recess 18 a of the female couplingshaft 18 are substantially equilateral triangular prism, but theconfigurations are not limited to this. For example, in an alternative,the recess 18 a may have a polygonal cross-section having odd numbersides, and the projection 17 a may be a deformed circle (such astriangle with rounded apices) having the same number of equilateralsides, and the projection 17 a may have prism edge lines, and theportion between the edge lines are concave toward the center, forexample, the cross-section is a grooved circle.

In the foregoing embodiment, the configurations of the projection 17 aof the male coupling shaft 17 and the recess 18 a of the female couplingshaft 18 may be such that only one of them is a twisted positive prismconfiguration.

In the foregoing embodiment, the drum flange 16 and the male couplingshaft 17 are integral with each other, but male coupling shaft 17 may bemanufactured separately, and then on the drum flange 16.

The examples of the projection 17 a will be described.

In FIG. 25, to the end of the male shaft 17, a substantially triangularpyramid projection 17 a is provided. In such a case, when the drivingforce is transmitted, the base portion of the projection 17 a can beabutted to the corner portions of the entrance of the hole since theentrance of the recess 18 a is substantially triangular. The projection17 a is not contacted to the inclined surface of the recess 18 a.

In FIG. 26, the end of the male shaft 17 is provided with a projection17 a which is substantially triangular prism 17 a 2, in shape, having atriangular pyramid end 17 a 1. In this example, the triangular prism 17a 2 portion is contacted to the corner of the entrance of the recess 18a. The triangular pyramid portion is not contacted to the inclinedsurface of the recess 18 a.

In FIG. 27, the projection 17 a is a substantially triangular prism, andthe edge lines are rounded. Referring to FIG. 28, another example of theprojection 17 a of the male coupling shaft 17 and the recess 18 a of thefemale coupling shaft 18, will be described.

In this embodiment, the configuration of the projection 17 a isnon-twisted rectangular prism, and the recess 18 a to be engaged by theprojection 17 a is a hole of twisted rectangular prism (FIG. 29). Thetwisting direction of the recess 18 a is opposite from the rotationaldirection toward the outside of the main assembly 13 from thephotosensitive drum 7 side. When the rotating force of the recess 18 ais transmitted to the projection 17 a after the projection 17 a and therecess 18 a provided in the main assembly 13 are engaged, the baseportion of the projection 17 a and the corners of the entrance of therecess 18 a are contacted so that driving force transmission is stable.

In this embodiment, the projection 17 a is rectangular prism, and therecess 18 a is twisted rectangular hole, but this is not inevitable, andanother prism configuration is usable. In the foregoing embodiments, thetwisting direction of the recess 18 a is opposite from the rotationaldirection of the gear from the entrance of the hole toward the depth.

The amount of the twisting of the hole (projection) is 1°-15° in therotational direction per axis length of 1 mm.

In this embodiment, the depth of the hole is approx. 4 mm, and theamount of the twisting is approx. 30°.

In the foregoing embodiments, the projection 17 a is not twisted.Therefore, the projection 17 a is contacted to the entrance of the hole18 a when the driving force is transmitted from the female shaft 18. Theprojection 17 a is not abutted to the inclined surface of the hole 18.By the engagement between the non-twisted projection 17 a and thetwisted hole 18 a, the hole 18 a is rotated. Then, the base portion ofthe projection 17 a is contacted to the entrance portion of the hole 18a by which the position thereof relative to the hole 18 is determined.The base portion has a higher strength than the other portion, andtherefore, the projection 17 a is not deformed. The neighborhood of thecorner portion of the projection 17 a and/or the corner portion of theentrance of the hole 18 a is slightly deformed locally, and bites intothe inner surface of the hole. Therefore, the coupling between therecess and the hole is firmer. This advantage is remarkable when theyare made of plastic resin material.

As will be understood from the foregoing, the projection may be providedin the main assembly, and the hole may be provided in the processcartridge.

As described in the foregoing, according to the present invention, thedriving force can be transmitted stably.

In this embodiment, the process cartridge B was described as a processcartridge which forms a monochromatic image, but the present inventionis applicable, with desirable effects, to a process cartridge whichcomprises a plurality of developing means for forming an image composedof a plurality of colors (for example, two toner image, three toneimages, full color image, or the like).

The electrophotographic photosensitive member does not need to belimited to the photosensitive drum 7. For example, the following typesmay be included. First, as for the photosensitive material,photoconductive material such as amorphous silicon, amorphous selenium,zinc oxide, titanium oxide, organic photoconductor, and the like, may beincluded. As for the configuration of the base member on whichphotosensitive material is placed, it may be in the form of a drum orbelt. For example, the drum type photosensitive member comprises acylinder formed of aluminum alloy or the like, and a photoconductorlayer deposited or coated on the cylinder.

As for the image developing method, various known methods may beemployed; for example, two-component magnetic brush type developingmethod, cascade type developing method, touch-down type developingmethod, cloud type developing method, and the like.

Also in this embodiment, a so-called contact type charging method wasemployed, but obviously, charging means with a structure different fromthe one described in this embodiment may be employed; for example, oneof the conventional structures, in which a tungsten wire is surroundedby a metallic shield formed of aluminum or the like, on three sides, andpositive or negative ions generated by applying high voltage to thetungsten wire are transferred onto the surface of a photosensitive drumto uniformly charge the surface of the photosensitive drum.

The charging means may be in the form of a blade (charge blade), a pad,a block, a rod, a wire, or the like, in addition to being in the form ofa roller.

As for the method for cleaning the toner remaining on the photosensitivedrum, a blade, a fur brush, a magnetic brush, or the like may beemployed as a structural member for the cleaning means.

As described in the foregoing, according to the present invention, thedriving force can be assuredly transmitted from the main assembly of anelectrophotographic image forming apparatus to the electrophotographicphotosensitive drum.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:
 1. A process cartridge detachably mountable to amain assembly of an electrophotographic image forming apparatus, whereinthe main assembly includes a motor, a driving rotatable member forreceiving driving force from the motor, and a hole defined by twistedsurfaces, the hole being substantially coaxial with said drivingrotatable member, said process cartridge comprising: anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a projection engageable with the twistedsurfaces, said projection being provided at a longitudinal end of saidphotosensitive drum, wherein said projection is non-twisted, and whenthe driving rotatable member rotates with the hole and said projectionengaged with each other, rotational driving force is transmitted fromthe driving rotatable member to said photosensitive drum throughengagement between the hole and said projection.
 2. A process cartridgeaccording to claim 1, wherein said projection is contacted to anentrance of the hole to transmit the driving force.
 3. A processcartridge according to claim 2, wherein said projection is not contactedto an inclined surface of the hole.
 4. A process cartridge according toclaim 1, 2 or 3, wherein the hole of the main assembly has asubstantially polygonal cross section, and said projection has asubstantially prism shape.
 5. A process cartridge according to claim 4,wherein the cross section of the hole is substantially triangular, andthe prism is a substantially triangular prism.
 6. A process cartridgeaccording to claim 4, wherein said prism has rounded edges.
 7. A processcartridge according to claim 1, 2 or 3, wherein the hole of the mainassembly has a substantially polygonal cross section, and saidprojection has a substantially pyramid shape.
 8. A process cartridgeaccording to claim 7, wherein the cross section is substantiallytriangular, and the pyramid is a triangular pyramid.
 9. A processcartridge according to claim 1, 2 or 3, wherein the hole of the mainassembly has a substantially polygonal cross section, and saidprojection has a substantially prism shape having a substantiallypyramid shape at its end.
 10. A process cartridge according to claim 9,wherein the prism is a substantially triangular prism, and the pyramidis a triangular pyramid.
 11. A process cartridge according to claim 1, 2or 3, wherein said projection is provided on a flange member, whereinsaid flange member includes an engaging portion for engaging an innersurface of said photosensitive drum and a shaft portion for supportingsaid drum on a cartridge frame, and said projection is provided at anend of said shaft portion.
 12. A process cartridge according to claim11, wherein said flange member is provided with a gear for transmittingdriving force to a developing roller as said process means.
 13. Aprocess cartridge according to claim 12, wherein said engaging portion,shaft portion, projection and gear are integrally molded from plasticresin material.
 14. A process cartridge according to claim 1, 2 or 3,wherein said process means includes at least one of a charging memberfor charging said photosensitive drum, a developing member fordeveloping a latent image formed on said photosensitive drum and acleaning member for removing toner remaining on said photosensitivedrum.
 15. A process cartridge detachably mountable to a main assembly ofan electrophotographic image forming apparatus for forming an image on arecording material, the main assembly including a motor, a drivingrotatable member for receiving driving force from said motor, and atwisted recess having a non-circular cross-section and substantiallycoaxial with a rotation axis of said driving rotatable member, saidprocess cartridge comprising: a rotatable electrophotographicphotosensitive drum; process means actable on said photosensitive drum;a projection provided at a longitudinal end of said photosensitive drum,having a non-circular cross-section and substantially coaxial with arotation axis of said photosensitive drum, wherein said projection isnon-twisted, and said projection of said photosensitive drum has such adimension and configuration that it can take a first relative rotationalposition with respect to the recess of the driving rotatable member inwhich relative rotational movement therebetween is permitted, and asecond relative rotational position with respect to the recess of thedriving rotatable member in which relative rotational movement isprevented in one rotational direction, while the rotation axis of thedriving rotatable member and the rotation axis of said photosensitivedrum are substantially aligned.
 16. A process cartridge according toclaim 15, wherein said projection is contacted to an entrance of therecess to transmit the driving force.
 17. A process cartridge accordingto claim 16, wherein said projection is not contacted to an inclinedsurface of the recess.
 18. A process cartridge according to claim 15, 16or 17, wherein the recess of the main assembly has a substantiallypolygonal cross section, and said projection has a substantially prismshape.
 19. A process cartridge according to claim 18, wherein the crosssection of the recess is substantially triangular, and the prism is asubstantially triangular prism.
 20. A process cartridge according toclaim 18, wherein said prism has rounded edges.
 21. A process cartridgeaccording to claim 15, 16 or 17, wherein the recess of the main assemblyhas a substantially polygonal cross section, and said projection has asubstantially pyramid shape.
 22. A process cartridge according to claim21, wherein the cross section of the recess is substantially triangular,and the pyramid is a triangular pyramid.
 23. A process cartridgeaccording to claim 15, 16 or 17, wherein the recess of the main assemblyhas a substantially polygonal cross section, and said projection has asubstantially prism shape having a substantially pyramid shape at itsend.
 24. A process cartridge according to claim 23, wherein the crosssection of the recess is substantially triangular, and the prism is asubstantially triangular prism, and the pyramid is a triangular pyramid.25. A process cartridge according to claim 15, 16 or 17, wherein saidprojection is provided on a flange member, wherein said flange memberincludes an engaging portion for engaging an inner surface of saidphotosensitive drum and a shaft portion for supporting said drum on acartridge frame, and said projection is provided at an end of said shaftportion.
 26. A process cartridge according to claim 25, wherein saidflange member is provided with a gear for transmitting driving force toa developing roller as said process means.
 27. A process cartridgeaccording to claim 26, wherein said engaging portion, shaft portion,projection and gear are integrally molded from plastic resin material.28. A process cartridge according to claim 15, 16 or 17, wherein saidprocess means includes at least one of a charging member for chargingsaid photosensitive drum, a developing member for developing a latentimage formed on said photosensitive drum and a cleaning member forremoving toner remaining on said photosensitive drum.
 29. Anelectrophotographic image forming apparatus for forming an image on arecording material, to which a process cartridge is detachablymountable, said apparatus comprising: (a) a motor; (b) a drivingrotatable member for receiving driving force from said motor; (c) a holedefined by twisted surfaces, said hole being substantially coaxial withsaid driving rotatable member; (d) a mounting member for detachablymounting a process cartridge, said process cartridge including: anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a projection engageable with said twistedsurfaces, said projection provided at a longitudinal end of saidphotosensitive drum, wherein when said projection is non-twisted, andwhen said main assembly driving rotatable member rotates with said holeand projection engaged with each other, rotational driving force istransmitted from said driving rotatable member to said photosensitivedrum through engagement between the hole and said projection; and (e) afeeding member for feeding the recording material.
 30. Anelectrophotographic image forming apparatus for forming an image on arecording material, to which a process cartridge is detachablymountable, said apparatus comprising: (a) a motor; (b) a drivingrotatable member for receiving driving force from said motor; (c) atwisted recess having a non-circular cross-section and substantiallycoaxial with a rotation axis of said driving rotatable member; (d) amounting member for detachably mounting a process cartridge, saidprocess cartridge including: a rotatable electrophotographicphotosensitive drum; process means actable on said photosensitive drum;a projection provided at a longitudinal end of said photosensitive drum,having a non-circular cross-section and substantially coaxial with arotation axis of said photosensitive drum, wherein said projection isnon-twisted, and said projection of said photosensitive drum has such adimension and configuration that it can take a first relative rotationalposition with respect to said recess of said driving rotatable member inwhich relative rotational movement therebetween is permitted, and asecond relative rotational position with respect to said recess of saiddriving rotatable member in which relative rotational movement isprevented in one rotational direction, while the rotation axis of saiddriving rotatable member and the rotation axis of said photosensitivedrum are substantially aligned; and (e) a feeding member for feeding therecording material.
 31. A process cartridge detachably mountable to amain assembly of an electrophotographic image forming apparatus, whereinsaid main assembly includes a motor, a driving rotatable member forreceiving driving force from the motor, and a non-twisted projection,the projection being substantially coaxial with the driving rotatablemember, said process cartridge comprising: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;and a hole defined by twisted surfaces, said hole being provided at alongitudinal end of said photosensitive drum, wherein, when the drivingrotatable member rotates with the projection and hole engaged with eachother, rotational driving force is transmitted from the drivingrotatable member to said photosensitive drum through engagement betweensaid hole and the projection.
 32. A process cartridge according to claim31, wherein the projection provided in the main assembly is contacted toan entrance of said hole to transmit the driving force.
 33. A processcartridge according to claim 32, wherein the projection provided in themain assembly is not contacted to an inclined surface of said hole. 34.A process cartridge according to claims 31, 32 or 33, wherein the holehas a substantially polygonal cross section, and the projection providedin the main assembly has a substantially prism shape.
 35. A processcartridge according to claim 34, wherein the cross section of the holeis substantially triangular, and the prism is a substantially triangularprism.
 36. A process cartridge according to claim 34, wherein the prismhas rounded edges.
 37. A process cartridge according to claim 31, 32 or33, wherein the hole has a substantially polygonal cross section, andthe projection provided in the main assembly has a substantially pyramidshape.
 38. A process cartridge according to claim 37, wherein the crosssection of the hole is substantially triangular, and the pyramid is atriangular pyramid.
 39. A process cartridge according to claim 31, 32 or33, wherein the hole has a substantially polygonal cross section, andthe projection provided in the main assembly has a substantially prismshape having a substantially pyramid shape at its end.
 40. A processcartridge according to claim 39, wherein the cross section of the holeis substantially triangular, and the prism is a substantially triangularprism, and the pyramid is a triangular pyramid.
 41. A process cartridgeaccording to claim 31, 32 or 33, wherein said hole is provided on aflange member, wherein said flange member includes an engaging portionfor engaging with an inner surface of said photosensitive drum and ashaft portion for supporting the drum on a cartridge frame, and saidhole is provided at an end of said shaft portion.
 42. A processcartridge according to claim 41, wherein said flange member is providedwith a gear for transmitting driving force to a developing roller assaid process means.
 43. A process cartridge according to claim 42,wherein said engaging portion, shaft portion, hole and gear areintegrally molded from plastic resin material.
 44. A process cartridgeaccording to claim 31, 32 or 33, wherein said process means includes atleast one of a charging member for charging said photosensitive drum, adeveloping member for developing a latent image formed on saidphotosensitive drum and a cleaning member for removing toner remainingon said photosensitive drum.
 45. A process cartridge detachablymountable to a main assembly of an electrophotographic image formingapparatus for forming an image on a recording material, the mainassembly including a motor, a driving rotatable member for receivingdriving force from the motor, and a non-twisted projection, theprojection being substantially coaxial with a rotation axis of thedriving rotatable member, said process cartridge comprising: a rotatableelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; a recess defined by twisted surfaces, said recessbeing provided at a longitudinal end of said photosensitive drum, andbeing substantially coaxial with a rotation axis of said photosensitivedrum, wherein said recess of said photosensitive drum has such adimension and configuration that it can take a first relative rotationalposition with respect to the projection of the driving rotatable memberin which relative rotational movement therebetween is permitted, and asecond relative rotational position with respect to the projection ofthe driving rotatable member in which relative rotational movement isprevented in one rotational direction, while the rotation axis of thedriving rotatable member and the rotation axis of said photosensitivedrum are substantially aligned.
 46. A process cartridge according toclaim 45, wherein the projection provided in the main assembly iscontacted to an entrance of the recess to transmit the driving force.47. A process cartridge according to claim 46, wherein the projectionprovided in the main assembly is not contacted to an inclined surface ofsaid recess.
 48. A process cartridge according to claim 45, 46 or 47,wherein the recess has a substantially polygonal cross section, and theprojection provided in the main assembly has a substantially prismshape.
 49. A process cartridge according to claim 48, wherein the crosssection of the recess is substantially triangular, and the prism is asubstantially triangular prism.
 50. A process cartridge according toclaim 48, wherein the prism has rounded edges.
 51. A process cartridgeaccording to claim 45, 46 or 47, wherein the recess has a substantiallypolygonal cross section, and the projection provided in the mainassembly has a substantially pyramid shape.
 52. A process cartridgeaccording to claim 51, wherein the cross section of the recess issubstantially triangular, and the pyramid is a triangular pyramid.
 53. Aprocess cartridge according to claim 45, 46 or 47, wherein the recesshas a substantially polygonal cross section, and the projection providedin the main assembly has a substantially prism shape having asubstantially pyramid shape at its end.
 54. A process cartridgeaccording to claim 53, wherein the cross section of the recess issubstantially triangular, and the prism is a substantially triangularprism, and the pyramid is a triangular pyramid.
 55. A process cartridgeaccording to claim 45, 46 or 47, wherein the recess is provided on aflange member, wherein the flange member includes an engaging portionfor engaging with an inner surface of said photosensitive drum and ashaft portion for supporting the drum on a cartridge frame, and therecess is provided at an end of the shaft portion.
 56. A processcartridge according to claim 55, wherein the flange member is providedwith a gear for transmitting driving force to a developing roller assaid process means.
 57. A process cartridge according to claim 56,wherein said engaging portion, shaft portion, recess and gear areintegrally molded from plastic resin material.
 58. A process cartridgeaccording to claim 45, 46 or 47, wherein said process means includes atleast one of a charging member for charging said photosensitive drum, adeveloping member for developing a latent image formed on saidphotosensitive drum and a cleaning member for removing toner remainingon said photosensitive drum.
 59. An electrophotographic image formingapparatus for forming an image on a recording material, to which aprocess cartridge is detachably mountable, said apparatus comprising:(a) a motor; (b) a driving rotatable member for receiving driving forcefrom said motor; (c) a non-twisted projection, which is substantiallycoaxial with said driving rotatable member; (d) a mounting member fordetachably mounting a process cartridge, said process cartridgeincluding: an electrophotographic photosensitive drum; process meansactable on said photosensitive drum; and a hole defined by twistedsurfaces, said hole being provided at a longitudinal end of saidphotosensitive drum, wherein when said driving rotatable member rotateswith said projection and hole engaged with each other, rotationaldriving force is transmitted from said driving rotatable member to saidphotosensitive drum through engagement between said hole and saidprojection; and (e) a feeding member for feeding the recording material.60. An electrophotographic image forming apparatus for forming an imageon a recording material, to which a process cartridge is detachablymountable, said apparatus comprising: (a) a motor; (b) a drivingrotatable member for receiving driving force from said motor; (c) anon-twisted projection which is substantially coaxial with said drivingrotatable member; (d) a mounting member for detachably mounting aprocess cartridge, said process cartridge including: a rotatableelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a recess defined by twisted surfaces, saidrecess being provided at a longitudinal end of said photosensitive drum,and being substantially coaxial with a rotation axis of saidphotosensitive drum, wherein said recess of said photosensitive drum hassuch a dimension and configuration that it can take a first relativerotational position with respect to said projection of said drivingrotatable member in which relative rotational movement therebetween ispermitted, and a second relative rotational position with respect tosaid projection of said driving rotatable member in which relativerotational movement is prevented in one rotational direction, while therotation axis of said driving rotatable member and the rotation axis ofsaid photosensitive drum are substantially aligned; and (e) a feedingmember for feeding the recording material.
 61. A process cartridgedetachably mountable to a main assembly of an electrophotographic imageforming apparatus, wherein the main assembly includes a motor, a drivingrotatable member for receiving driving force from the motor, and anon-twisted hole, the hole being substantially coaxial with the drivingrotatable member, said process cartridge comprising: anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted projection engageable with the hole,said projection being provided at a longitudinal end of saidphotosensitive drum, wherein when the driving rotatable member rotateswith the hole and projection engaged with each other, rotational drivingforce is transmitted from the driving rotatable member to saidphotosensitive drum through engagement between the hole and saidprojection.
 62. A process cartridge according to claim 61, wherein thehole of the main assembly has a substantially polygonal cross section,and said projection has a substantially prism shape.
 63. A processcartridge according to claim 62, wherein the cross section of the holeis substantially triangular, and the prism is a substantially triangularprism.
 64. A process cartridge according to claim 61, wherein the holeof the main assembly has a substantially polygonal cross section, andsaid projection has a substantially pyramid shape.
 65. A processcartridge according to claim 64, wherein the cross section of the holeis substantially triangular, and the pyramid is a triangular pyramid.66. A process cartridge according to claim 62 or 63, wherein the prismhas rounded edges.
 67. A process cartridge according to claim 61,wherein said projection is provided on a flange member, wherein saidflange member includes an engaging portion for engaging with an innersurface of said photosensitive drum and a shaft portion for supportingthe drum on a cartridge frame, and said projection is provided at an endof said shaft portion.
 68. A process cartridge according to claim 67,wherein said flange member is provided with a gear for transmittingdriving force to a developing roller as said process means.
 69. Aprocess cartridge according to claim 68, wherein said engaging portion,shaft portion, projection and gear are integrally molded from plasticresin material.
 70. A process cartridge according to claim 61, whereinsaid process means includes at least one of a charging member forcharging said photosensitive drum, a developing member for developing alatent image formed on said photosensitive drum and a cleaning memberfor removing toner remaining on said photosensitive drum.
 71. A processcartridge according to claim 1, 15, 31, 45 or 61, wherein the drivingrotatable member provided in the main assembly comprises a gear.
 72. Aprocess cartridge according to claim 1, 15, 31, 45 or 61, wherein theimage forming apparatus further comprises: an openable member which isopenable and closable when said process cartridge is mounted to ordemounted from the main assembly, and a movable member for moving saiddriving rotatable member in an axial direction of said driving rotatablemember away from a process cartridge mounting position in interrelationwith an opening operation of said openable member and for moving saiddriving rotatable member in the axial direction of said drivingrotatable member toward the process cartridge mounting position ininterrelation with a closing operation of said openable member.
 73. Anelectrophotographic image forming apparatus for forming an image on arecording material, to which a process cartridge is detachablymountable, said apparatus comprising: (a) a motor; (b) a drivingrotatable member for receiving driving force from said motor; (c) anon-twisted hole which is substantially coaxial with said drivingrotatable member; (d) a mounting member for detachably mounting aprocess cartridge, said process cartridge including: anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted projection engageable with said hole,said projection being provided at a longitudinal end of saidphotosensitive drum, wherein when said driving rotatable member rotateswith said hole and projection engaged with each other, rotationaldriving force is transmitted from said driving rotatable member to saidphotosensitive drum through engagement between said hole and saidprojection; and (e) a feeding member for feeding the recording material.74. An image forming apparatus according to claim 29, 30, 59, 60 or 73,wherein said driving rotatable member comprises a gear.
 75. An imageforming apparatus according to claim 29, 30, 59, 60 or 73, wherein saidimage forming apparatus further comprises: an openable member which isopenable and closable when said process cartridge is mounted to ordemounted from the main assembly, and a movable member for moving saiddriving rotatable member in an axial direction of said driving rotatablemember away from a process cartridge mounting position in interrelationwith an opening operation of said openable member and for moving saiddriving rotatable member in the axial direction of said drivingrotatable member toward the process cartridge mounting position ininterrelation with a closing operation of said openable member.
 76. Aprocess cartridge detachably mountable to a main assembly of anelectrophotographic image forming apparatus, wherein the main assemblyincludes a motor, a driving rotatable member for receiving driving forcefrom the motor, and a hole defined by twisted surfaces, the hole beingsubstantially coaxial with said driving rotatable member, said processcartridge comprising: an electrophotographic photosensitive drum; acharging member for charging said photosensitive drum; a developingmember for developing a latent image formed on said photosensitive drum;a cleaning member for removing toner remaining on said photosensitivedrum; and a projection engageable with the twisted surfaces, saidprojection being provided at a longitudinal end of said photosensitivedrum, wherein said projection is non-twisted, and when the drivingrotatable member rotates with the hole and the projection engaged witheach other, rotational driving force is transmitted from the drivingrotatable member to said photosensitive drum through engagement betweenthe hole and said projection, and wherein said projection is contactedto an entrance of the hole to transmit the driving force, and saidprojection is not contacted to an inclined surface of the hole, andwherein said projection has a substantially prism shape.
 77. A processcartridge according to claim 76, wherein the hole has a substantiallytriangular cross section, and the prism is a substantially triangularprism.
 78. A process cartridge according to claim 76 or 77, wherein saidprism has rounded edges.
 79. A process cartridge according to claim 76or 77, wherein said projection is provided on a flange member, whereinsaid flange member includes an engaging portion for engaging an innersurface of said photosensitive drum and a shaft portion for supportingsaid drum on a cartridge frame, and said projection is provided at anend of said shaft portion.
 80. A process cartridge according to claim79, wherein said flange member is provided with a gear for transmittingdriving force to a developing roller as said process means.
 81. Aprocess cartridge according to claim 80, wherein said engaging portion,shaft portion, projection and gear are integrally molded from plasticresin material.
 82. An electrophotographic image forming apparatus forforming an image on a recording material, to which a process cartridgeis detachably mountable, said apparatus comprising: (a) a motor; (b) adriving rotatable member for receiving driving force from said motor;(c) a hole defined by twisted surfaces, said hole being substantiallycoaxial with said driving rotatable member; (d) a mounting member fordetachably mounting a process cartridge, said process cartridgeincluding: an electrophotographic photosensitive drum; a charging memberfor charging said photosensitive drum; a developing member fordeveloping a latent image formed on said photosensitive drum; a cleaningmember for removing toner remaining on said photosensitive drum; and aprojection engageable with the twisted surfaces, said projection beingprovided at a longitudinal end of said photosensitive drum, wherein saidprojection is non-twisted, and when the driving rotatable member rotateswith the hole and projection engaged with each other, rotational drivingforce is transmitted from the driving rotatable member to saidphotosensitive drum through engagement between the hole and saidprojection, and wherein said projection is contacted to an entrance ofthe hole to transmit the driving force, and said projection is notcontacted to an inclined surface of the hole, and wherein saidprojection has a substantially prism shape; and (e) a feeding member forfeeding the recording material.
 83. A driving force transmitting partfor an electrophotographic image forming apparatus for forming an imageon a recording material, a main assembly of the apparatus including amotor, a driving rotatable member for transmitting a driving force fromthe motor, and a twisted hole formed in the driving rotatable member ata central portion thereof and having a non-circular cross section with aplurality of corner portions, said driving force transmitting partcomprising: a mounting portion for mounting said driving forcetransmitting part to an electrophotographic photosensitive drum; and anon-twisted projection extending from said mounting portion and having anon-circular cross section with a plurality of corner portions, saidprojection being engageable with the twisted hole of said drivingrotatable member to receive the driving force, for rotating theelectrophotographic photosensitive drum, from the main assembly whensaid driving force transmitting part is mounted to the main assembly.84. A driving force transmitting part according to claim 83, furthercomprising a columnar shaft for supporting the electrophotographicphotosensitive drum on a frame, and a drum gear for transmitting to adeveloping roller the driving force received from said driving rotatablemember, wherein said projection is provided at an end of said shaft, andwherein said shaft is provided at a central portion of said drum gear.85. A driving force transmitting part for transmitting a driving forceto an electrophotographic photosensitive drum and to a developing rollerfor developing a latent image formed on the photosensitive drum, whereinthe photosensitive drum and the developing roller are contained in aprocess cartridge which is detachably mountable to a main assembly of anelectrophotographic image forming apparatus which includes a motor, amain assembly gear for transmitting a driving force from the motor, anda twisted hole formed in the main assembly gear at a central portionthereof and having a substantially triangular cross section, saiddriving force transmitting part comprising: a drum gear for transmittingthe driving force received from said main assembly to the developingroller when the process cartridge is mounted to the main assembly; ashaft provided at a central portion of said drum gear; and a non-twistedprojection in the form of a substantially triangular prism provided atan end of said shaft and which is engageable with the twisted hole ofthe main assembly to receive the driving force from the main assemblywhen the process cartridge is mounted to the main assembly.
 86. Adriving force transmitting part according to claim 84 or 85, whereinsaid projection, said drum gear, and said shaft are composed ofintegrally molded resin material.
 87. A driving force transmitting partaccording to claim 83, 84 or 85, wherein the cross section of thetwisted hole is in the form of a substantially equilateral triangle, andwherein said projection is in the form of a substantially equilateraltriangular prism, and corner portions of said projection are beveled.88. A driving force transmitting part according to claim 85, wherein thecross section of the twisted hole is in the form of a substantiallyequilateral triangle, and wherein said projection is in the form of asubstantially equilateral triangular prism with beveled corner portions.89. An electrophotographic photosensitive drum for anelectrophotographic image forming apparatus for forming an image on arecording material, the apparatus including a motor, a driving rotatablemember for transmitting a driving force from the motor, and a twistedhole formed in the driving rotatable member at a central portion thereofand having a non-circular cross section with a plurality of cornerportions, said electrophotographic photosensitive drum comprising: acylindrical member having a photosensitive layer on a circumferentialsurface thereof; and a non-twisted projection provided at an end of saidcylindrical member, said projection having a non-circular cross sectionwith a plurality of corner portions and being engageable with thetwisted hole for receiving the driving force from said driving rotatablemember, wherein when said electrophotographic photosensitive drum ismounted to a main assembly of the image forming apparatus, saidprojection is engaged with the twisted hole to receive the driving forcefor rotating said electrophotographic photosensitive drum.
 90. Anelectrophotographic photosensitive drum according to claim 89, furthercomprising a columnar shaft for supporting said electrophotographicphotosensitive drum on a frame, and a drum gear for transmitting to adeveloping roller the driving force received from said driving rotatablemember, wherein said projection is provided at an end of said shaft, andwherein said shaft is provided at a central portion of said drum gear.91. An electrophotographic photosensitive drum for a process cartridgedetachably mountable to a main assembly of an electrophotographic imageforming apparatus for forming an image on a recording material, the mainassembly including a motor, a main assembly gear for transmitting adriving force from the motor, and a twisted hole formed in the mainassembly gear at a central portion thereof and having a substantiallytriangular cross section, said electrophotographic photosensitive drumcomprising: a. a cylindrical member having a photosensitive layer on acircumferential surface thereof; and b. a driving force transmittingpart mounted to an end of said cylindrical member, said transmittingpart including: a drum gear for transmitting the driving force from themain assembly to a developing roller when said electrophotographicphotosensitive drum is mounted to the main assembly; a shaft provided ata center of said drum gear; and a non-twisted projection in the form ofa substantially triangular prism provided at an end of said shaft, forengaging with the twisted hole to receive the driving force from themain assembly when said electrophotographic photosensitive drum ismounted to the main assembly, wherein said driving force transmittingpart receives the driving force from the main assembly throughengagement between the twisted hole and said projection and transmitsthe driving force to said electrophotographic photosensitive drumthrough said shaft and to the developing roller through said drum gear.92. An electrophotographic photosensitive drum according to claim 90 or91, wherein said projection, said drum gear, and said shaft are composedof integrally molded resin material.
 93. An electrophotographicphotosensitive drum according to claim 89, 90 or 91, wherein the crosssection of the twisted hole is in the form of a substantiallyequilateral triangle, and wherein said projection is in the form of asubstantially equilateral triangular prism, and the corner portions ofsaid projection are beveled.
 94. An electrophotographic photosensitivedrum according to claim 91, wherein the cross section of the twistedhole is in the form of a substantially equilateral triangle, and whereinsaid projection is in the form of a substantially equilateral triangularprism with beveled corner portions.
 95. A driving force transmittingpart for transmitting a driving force to an electrophotographicphotosensitive drum and to a developing roller for developing a latentimage formed on the photosensitive drum, wherein said driving forcetransmitting part is mountable to a main assembly of anelectrophotographic image forming apparatus which includes a motor, amain assembly gear for transmitting a driving force from the motor, anda hole defined by twisted surfaces, the hole being substantially coaxialwith said main assembly gear, said driving force transmitting partcomprising: a drum gear for transmitting the driving force received fromthe main assembly to the developing roller when said driving forcetransmitting part is mounted to the main assembly; a shaft provided at acentral portion of said drum gear; and a projection engageable with thetwisted surfaces, said projection being provided at an end of saidshaft, wherein said projection is non-twisted, and when the mainassembly gear rotates with the hole and said projection engaged witheach other, rotational driving force is transmitted from the mainassembly gear to said photosensitive drum through engagement between thehole and said projection.
 96. A driving force transmitting partaccording to claim 95, wherein the hole of the main assembly has asubstantially polygonal cross section, and said projection has asubstantially prism shape.
 97. A driving force transmitting partaccording to claim 96, wherein the cross section of the hole issubstantially triangular, and the prism is a substantially triangularprism.
 98. A driving force transmitting part according to claim 96 or97, wherein said prism has rounded edges.
 99. A driving forcetransmitting part according to claim 98, wherein said projection isprovided on a flange member, wherein said flange member includes anengaging portion for engaging an inner surface of the photosensitivedrum and said shaft, which is for supporting the photosensitive drum ona cartridge frame, and said projection is provided at an end of saidshaft.
 100. A driving force transmitting part according to claim 99,wherein said flange member is provided with said drum gear.
 101. Adriving force transmitting part according to claim 100, wherein saidengaging portion, shaft, projection and drum gear are integrally moldedfrom plastic resin material.
 102. A driving force transmitting partaccording to claim 95, wherein the hole of the main assembly has asubstantially polygonal cross section, and said projection has asubstantially pyramid shape.
 103. A driving force transmitting partaccording to claim 102, wherein the cross section of the hole issubstantially triangular, and the pyramid is a triangular pyramid. 104.A driving force transmitting part according to claim 95, wherein thephotosensitive drum and the developing roller are contained in a processcartridge that is detachably mountable to the main assembly, and whereinsaid driving force transmitting part is mounted by mounting the processcartridge to the main assembly.
 105. An electrophotographicphotosensitive drum for a main assembly of an electrophotographic imageforming apparatus for forming an image on a recording material, the mainassembly including a motor, a main assembly gear for transmitting adriving force from the motor, and a hole defined by twisted surfaces,the hole being substantially coaxial with the main assembly gear, saidelectrophotographic photosensitive drum comprising: a. a cylindricalmember having a photosensitive layer on a circumferential surfacethereof; and b. a driving force transmitting part mounted to an end ofsaid cylindrical member, said transmitting part including: a drum gearfor transmitting the driving force from the main assembly to adeveloping roller when said electrophotographic photosensitive drum ismounted to the main assembly; a shaft provided at a center of said drumgear; and a projection engageable with the twisted surfaces, saidprojection being provided at an end of said shaft, wherein saidprojection is non-twisted, and when the main assembly gear rotates withthe hole and said projection engaged with each other, rotational drivingforce is transmitted from the main assembly gear to the photosensitivedrum through engagement between the hole and said projection.
 106. Aphotosensitive drum according to claim 105, wherein the hole of the mainassembly has as substantially polygonal cross section, and saidprojection has a substantially prism shape.
 107. A photosensitive drumaccording to claim 106, wherein the cross section of the hole issubstantially triangular, and the prism is a substantially triangularprism.
 108. A photosensitive drum according to claim 106 or 107, whereinsaid prism has rounded edges.
 109. A photosensitive drum according toclaim 108, wherein said projection is provided on a flange member,wherein said flange member includes an engaging portion for engaging aninner surface of said photosensitive drum and said shaft, which is forsupporting said photosensitive drum on a cartridge frame, and saidprojection is provided at an end of said shaft.
 110. A photosensitivedrum according to claim 109, wherein said flange member is provided withsaid drum gear.
 111. A photosensitive drum according to claim 110,wherein said engaging portion, shaft, projection and drum gear areintegrally molded from plastic resin material.
 112. A photosensitivedrum according to claim 105, wherein the hole of the main assembly has asubstantially polygonal cross section, and said projection has asubstantially pyramid shape.
 113. A photosensitive drum according toclaim 112, wherein the cross section of the hole is substantiallytriangular, and the pyramid is a triangular pyramid.
 114. Aphotosensitive drum according to claim 105, wherein said photosensitivedrum and the developing roller are contained in a process cartridge thatis detachably mountable to the main assembly, and wherein saidphotosensitive drum is mounted by mounting the process cartridge to themain assembly.